Three-dimensional printing, also known as Additive manufacturing, is a process of making a three-dimensional solid object from a digital model of virtually any shape. Many three-dimensional printing technologies use an additive process in which successive layers of the part are built on top of previously deposited layers. Some of these technologies use inkjet printing, where one or more printheads eject successive layers of material. Three-dimensional printing is distinguishable from traditional object-forming techniques, which mostly rely on the removal of material from a work piece by a subtractive process, such as cutting or drilling.
The production of a three-dimensional object with these printers can require hours or, with some objects, even days to produce the object. One issue that arises in the production of three-dimensional objects with a three-dimensional printer is consistent functionality of the ejectors in the printheads that eject the drops of material that form the objects. During printing of an object, one or more ejectors can deteriorate by ejecting the material at an angle, rather than normal, to the printhead, ejecting drops that are smaller than an ejector should eject, or by failing to eject any drop at all. An ejector suffering from any of these operational deficiencies is known as an inoperative ejector. If the operational status of one or more ejectors deteriorates during the printing of the object, the quality of the printed object cannot be assessed until the printing operation is completed. Consequently, print jobs requiring many hours or multiple days can produce objects that do not conform to specifications due to inoperative ejectors in the printheads. Once such objects are detected, the printed objects are scrapped, restorative procedures are applied to the printheads to restore ejector functionality, and the print job is repeated. Consequently, improvements to three-dimensional object printers that enable identification of inoperable ejectors during a printing operation to enable correction of the inoperable ejectors without incurring a loss of partially printed objects would be beneficial.